Neurotransmitter

neurotransmitter

[noor″o-trans´mit-er]

a substance (e.g., norepinephrine, acetylcholine, dopamine) that is released from the axon terminal of a presynaptic neuron on excitation, and that travels across the synaptic cleft to either excite or inhibit the target cell.

neu·ro·trans·mit·ter

(nū'rō-trans'mit-ĕr),

Any specific chemical agent (including acetylcholine, five amines, four amino acids, two purines, and more than 28 peptides) released by a presynaptic cell, on excitation, that crosses the synapse to stimulate or inhibit the postsynaptic cell. More than one may be released at any given synapse. The neurotransmitters released by presynaptic cells may modulate transmitter release from presynaptic cells. Nitric oxide may be a retrograde neurotransmitter, released from postsynaptic cells, to act on presynaptic cells.

[neuro- + L. transmitto, to send across]

neurotransmitter

/neu·ro·trans·mit·ter/ (-tranz´mit-er) a substance released from the axon terminal of a presynaptic neuron on excitation, which diffuses across the synaptic cleft to either excite or inhibit the target cell.

false neurotransmitter an amine that can be stored in and released from presynaptic vesicles but that has little effect on postsynaptic receptors.

neurotransmitter

(no͝or′ō-trăns′mĭt-ər, -trănz′-, nyo͝or′-)

n.

A chemical substance, such as acetylcholine or dopamine, that transmits nerve impulses across a synapse.

neurotransmitter

[-transmit′ər]

Etymology: Gk, neuron + L, transmittere, to transmit

a chemical that modifies or results in the transmission of nerve impulses between synapses. Neurotransmitters are released from synaptic knobs into synaptic clefts and bridge the gap between presynaptic and postsynaptic neurons. Each vesicle within a synaptic knob stores as many as 10,000 neurotransmitter molecules. When a nerve impulse reaches a synaptic knob, thousands of neurotransmitter molecules squirt into the synaptic cleft and bind to specific receptors. This flow allows an associated diffusion of potassium and sodium ions that causes an action potential. Excitatory neurotransmitters decrease the negativity of postsynaptic membrane potentials; inhibitory neurotransmitters increase such potentials. Kinds of neurotransmitters include acetylcholine,gamma-aminobutyric acid, and norepinephrine.

neurotransmitter

Neurosynaptic transmitter Physiology Any of a number of small neuroregulating molecules–eg, catecholamines and acetylcholine, which are synthesized in the presynaptic terminals of neurons, stored in vesicles, and cause rapid and transient depolarization near their point of release in the synaptic cleft, where it stimulates production of either excitatory or inhibitory postsynaptic potentials; neurotransmission at synapses or neuromuscular junctions is due to binding of a neurotransmitter to its cognate receptor. See Amino acid neurotransmitter, Neuropeptide, Neuroregulator. Cf Hormone.

neu·ro·trans·mit·ter

(nūr'ō-trans'mit-ĕr)

Any specific chemical agent released by a presynaptic cell, on excitation, which crosses the synapse to stimulate or inhibit the postsynaptic cell.

[neuro- + L. transmitto, to send across]

neurotransmitter

Neurotransmitter

A chemical in the brain that transmits messages between neurons, or nerve cells. Changes in the levels of certain neurotransmitters, such as serotonin, norepinephrine, and dopamine, are thought to be related to bipolar disorder.

neurotransmitter

a substance which is formed in a neuron cell body and passes down the axon to be stored in vesicles in the axon terminals. It is released in response to action potentials, to act at a synapse with another neuron or at an effector site: skeletal muscle, smooth muscle or gland. See alsoacetylcholine, neuromuscular junction, noradrenaline.

neurotransmitter

a chemical agent, released from a presynaptic cell on excitation, which crosses the synaptic cleft to stimulate or inhibit the postsynaptic cell

neurotransmitter (nerˈ·ō·transˑ·mi·ter),

n chemical messenger that modifies or affects communication across synapses or neuromuscular connections. Important neurotransmitters include dopamine, serotonin, and acetylcholine.

neurotransmitter

A substance stored in the synaptic vesicles that is released when the axon terminal is excited by a nervous impulse. The substance then travels across the synaptic cleft to either excite or inhibit another neuron. This is accomplished by either decreasing the negativity of postsynaptic potentials (excitation), or increasing the negativity of postsynaptic potentials (inhibition). Common neurotransmitters include acetylcholine, dopamine, endorphins, adrenaline (epinephrine), gamma-aminobutyric acid (GABA), amino acids, such as glutamate and glycine, noradrenaline (norepinephrine), serotonin and substance P. Common neurotransmitters in the retina are glutamate (the primary excitatory neurotransmitter), GABA (inhibitory), glycine (inhibitory), dopamine (excitatory) and acetylcholine (excitatory). Seeneuron; synapse.

neu·ro·trans·mit·ter

(nūr'ō-trans'mit-ĕr)

Any specific chemical agent released by a presynaptic cell that, on excitation, crosses synapse to stimulate or inhibit the postsynaptic cell.

[neuro- + L. transmitto, to send across]

neurotransmitter,

n any one of numerous chemicals that modify or result in the transmission of nerve impulses between synapses. Neurotransmitters are released from synaptic knobs into synaptic clefts and bridge the gap between presynaptic and postsynaptic neurons.

Neuron.

neurotransmitter

a substance (e.g. norepinephrine, acetylcholine, dopamine) that is released from the axon terminal of a presynaptic neuron on excitation, and which travels across the synaptic cleft to either excite or inhibit the target cell.

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